presentation.getSaveToPdfOption().setThreadsCount(1); 

Presentation ppt = new Presentation();
ppt.loadFromFile(inputFile);
String text = "create, read";
PortionEx textRange=ppt.getSlides().get(0).FindFirstTextAsRange(text);
textRange.getFill().setFillType(FillFormatType.SOLID);
textRange.getFill().getSolidColor().setColor(Color.red);
textRange.setFontHeight(28);
textRange.setLatinFont(new TextFont("Arial"));
textRange.isBold(TriState.TRUE);
textRange.isItalic(TriState.TRUE);
textRange.setTextUnderlineType(TextUnderlineType.DOUBLE);
textRange.setTextStrikethroughType(TextStrikethroughType.SINGLE);
ppt.saveToFile(outputFile, FileFormat.PPTX_2016);
ppt.dispose();

ArrayList embedFonts = ppt.getEmbedFonts();

Presentation ppt = new Presentation();
// Load a PowerPoint presentation from the specified file.
ppt.loadFromFile(inputFile);
// Create a new object to store the default text range formatting properties.
PortionFormatEx format = new PortionFormatEx();
// Set the IsBold property of the text range formatting to true, making the text bold.
format.isBold(TriState.TRUE);
// Set the FillType property of the text range fill to Solid, indicating a solid fill color.
format.getFill().setFillType(FillFormatType.SOLID);
// Set the Color property of the solid fill color to red.
format.getFill().getSolidColor().setColor(Color.red);
// Set the FontHeight property of the text range formatting to 25, indicating the font size.
format.setFontHeight(25);
format.isBold(TriState.TRUE);

// Replace all occurrences of the text "Spire.Presentation for .NET" with "Spire.PPT" and apply the specified formatting.
ppt.ReplaceAndFormatText("Spire.Presentation for .NET", "Spire.PPT", format);

// Save the modified presentation to the specified output file in the PPTX format compatible with PowerPoint 2016.
ppt.saveToFile(outputFile, FileFormat.PPTX_2016);
// Dispose of the Presentation object to free up resources
ppt.dispose();